Benzoxazine-crosslinked waterborne polyurethane coatings for corrosion protection and emulsion separation

To overcome the limitations of waterborne polyurethane (WPU) in practical applications, including insufficient mechanical strength, poor water resistance, and weak adhesion, a series of multifunctional benzoxazine-modified WPU coatings were developed. A siloxane-containing dihydroxy benzoxazine was employed as a reactive chain extender, while perfluorodecyltriethoxysilane-modified TiO 2 nanoparticles (F-TiO 2 ) were introduced as functional nanofillers. During thermal curing, the ring-opening polymerization of benzoxazine moieties formed a crosslinked network within the polyurethane matrix, improving the mechanical properties, adhesion, and water resistance of the coatings. The optimized coating exhibited a tensile strength of 25.09 ± 0.75 MPa and an adhesion strength of 11.51 ± 0.23 MPa, accompanied by a low water absorption of 6%. Moreover, the synergistic effect of the hierarchical micro/nano-scale roughness generated by F-TiO 2 and the low-surface-energy fluorinated groups endowed the coating with superhydrophobicity, achieving a water contact angle (WCA) of 151° and self-cleaning capability. Furthermore, the coating exhibited anticorrosion performance, with a corrosion rate as low as 2.50 × 10 −5 mm·a −1 . When deposited onto melamine foam, the coating enabled efficient oil adsorption and continuous oil-water emulsion separation. This study provides a facile and effective strategy for the fabrication of high-performance multifunctional WPU coatings with promising applications in corrosion protection and oil-water separation.